Silver or Silverplate? Cup...

[crwecko]

I have recently purchased a cup and was told it is sterling silver that I was told was swedish. It has a T on the bottom and right below the T is the number 100. The T100 has a line going around to enclose the T followed by the 100 directly underneath it. Can anyone determine what year it's from and whether it's really sterling silver and whether it is really from Sweden?